Shock absorber



oct. 29, 1946. Y -G, M, MAGRUM 2,410,176

SHOCK ABSORBER Filed Oct. 1943 y 3 Sheets-Sheet l l l s N .J Q

Q l Si l u im u w N Q( N l .Q53 D Q s N Q I l I f Q o N A lg /f YN 65e w16: Amel/H.

G. M. MAGRUM sHoCKVABsoRBER Oct. 29, 1946.

Filed Oct. '7, 1943 3 Sheets-Sheet 2 Oct. 29, 1946. G. M. MAGRUM 2,410,176

SHOCK ABSORBER Filed oct. `"I, 1945 s sheets-sheet 5 @fev/76E Mael/M.

au s WE- Patented oct. 29, 1946 SHOCK ABSORBER A v Gervase M. Magrum, Buffalo, N. Y., assigner to Houdaille-Hershey Corporation, Detroit, a corporationrof Michigan Mich.,

Application October 7, 1943, Serial No. 505,286

This invention relates to hydraulic shock absorbers, particularly to the direct action type in which a cylinder structure and a pistonstructure are relatively reciprocable` longitudinally for displacement of fluid against flow resistance. In the use of such shock absorbers, as for-example for damping purposes in airplane landing gears or on guns for dampening the recoil, efficient operation of the shock absorber requires that the space in which the piston operates be at all times kept lled with hydraulic fluid to the exclusion of air, and compensating means should be provided to compensate for increase or decrease of the volume of the uid due to temperature changes and also to compensate for displacement of hydraulic fluid by the volume of the piston rod as it enters r leaves the cylinder. l

It is the object oi' my invention to provide an improved structure and arrangement Afor compensating for fluid volume variation due to temperature variation and forvvolume displacement by the piston rod in order that the cylinder space in which the piston operates may at al1 times be lrlept fully replenished and filled with hydraulic uid.

3' Claims. (Cl. 188-'-'88) More in detail, an important object is to pro-k I vide within the shock absorber an expansible and contractible enclosure for medium such as air, which enclosure is subjected to the pressure of the displaced hydraulic fluid and functions to counteract such pressure in order to keep filled at all times thespace within which the piston operates.

Another objectvof my invention is to provide for filling of hydraulic uid into the cylinder under sufiicient vpressure to reduce the Volume of the compensating structure an amount equal to the reduction in volume of fluid under the maximum temperature diierential anticipated in order that, under temperature variation and increase or decreaseA of the fluid volume in the cylinder, the compensator structure may contract or ex pand correspondingly to effect compensation and keep the cylinder fully lled. v

The various features of my invention are embodied in the structure shown on the drawings, in

which;y

Figure 1 is a longitudinal diametral section of Figure 4 is a1ngitudina1diametraisecnoa of 2 one end of a shock absorber showing a modied arrangement for the compensating structure and its condition Vwhen the piston is at an intermedi-'-` ate position in the cylinder; I l

Figure 5 is a view similar to Figure 4 showing a modified valving arrangement for control of displaced hydraulic fluid; n

Figure 6 is a longitudinal diametral section of one end of a shock absorber showing a modified form of compensating structure and the condition of such structure when the piston is at an intermediate point in the cylinder; and g Figure 7 is a view ysimilar toFigure 6 showing the condition of the compensating structure the piston is at the inner end of its 'stroke.

In the structure on Figures 1 to 3, the cylinder I0 is in the form of a length of metal tubing closed at its ends by outer and inner heads II and l2 respectively, these yheads being securedA to the cylinder by screwthreading into the yrespective ends thereof. K Y

The piston I3 within the vcylinder has the rod I4 extending therefrom through the head I2 and is secured at its outer end to a connector iitting I5, a protecting skirt I6 extending from the fitting to surround the cylinder I0. The cylinder head I2 supports suitable Aoil seal or packing means I'I/ for preventing leakage from the'cylinder I0 to the exterior. l

The piston I3 has ports I8 therethrough con!- trolled by a Yvalve disk I9 whichhas metering oriiices 20 in alignment with the ports and which is axially shiftable on the piston rod between the piston and an abutment'washer 2l engaging the shoulder 22 on the piston rod.

In the outer end of the cylinder I0 are located.

The cylinder head I I has the bore 24 in its inner side communicating with an inlet passageway 25 in which is seated a valve plug 26 terminating in a nipple p21 for connection with a Dump for charging hydraulic fluid into the cylinder, a check valve 28 engaged by a spring 29 permitting in-v flow but checking outflow. When the shock absorber is to be conditioned for service, the

piston is moved toits outermost position and hydraulic fluid is forced' in through the nipple under pressure sufficient to effect an initialjreduction in volume of the compensator structures C and the air therein an amount equal to the reduction in volume of iiuid under the maximum temperature differential anticipated during service of the shock absorber so that, under tem-` perature variation and increase or decrease of the uid volume in the cylinder, the compensator structure may contract or expand correspondingly to eifect compensation and keep the cylinder fully filled. Figure 3 shows the initial conand fitting I5 respectively providing means for,`

attaching the head and the fitting respectively to the relatively movable structures to be controlled. Figure 1 shows the piston having been moved into an intermediate position, such inward movement having been comparatively free as the valve disk I9 was moved away from the ports I8 for comparatively free flow of the hydraulic fluid from the outer end of thecylinder to the inner end thereof. Upon such inward movement of the piston, corresponding inward.l movement of the piston rod I4 displaces a corresponding volume of fluid resulting in corresponding contraction of the compensator structures C by the fluid pressure, Figure 2 showing the piston having moved inthe full distance for further contraction of the compensating structures. The expansion tendency of the compensating structures counteracts the contracting pressure and the cylinder is thus kept. filled with fluid. Upon outward or rebound movement ofthe piston, vthe valve disk will be closed and only the orifices 2B will be available for flow of fluid from the inner end of the cylinder to the outer end thereon-and as the piston rod withdraws its volume from the cylinder, the compensator structures C will expand and compensate for this decreasing volume so that the cylinder will be kept filled with oil during the outward movement of the piston.

As a result of the initial compression and contraction of the compensatorstructures when the fluid under pressure is charged into the cylinder, the compensator structures may expand to keep the cylinder filled with fluid while the temperature decreases within the temperature differential anticipated,`and under increasing temperature the compensatorfstructures will be further compressed and contracted so that compensation will be efficiently performed within the predetermined temperature range and at the same time the displacement by the piston rod of the duid in the cylinder will be compensated for.

The arrangement shown on Figure 4 is substantially the same as that shown on Figures 1 to 3 except that between the head II and the cylinder il! a cylindrical housing 32 is interposed to provide the chamber 33. The head II threads info thecuter end of the housing 32 and the housing has the annular threaded neck 34 threadingr into the outer end of the cylinder I0. Within the chamber 33 is the compensator structure C. the head I I having the valve nipple structure 2B app'ied thereto for charging of hydraulic fiuid under pressure into the chamber 33 and the cylinder I0 when the piston is at the outer endv of its stroke. As the piston now moves in and out during service of the vshock absorber, the compensator structure will function to correspondingly contract and expand to compensate for'volume displacement by the vpiston rod I4 and also to compensate for volume variation due to temperature changes. 4 When thepistonrnoves 4 inwardly during compression or bound operation of the shock absorber, the valve disk I9 will be open for comparatively 'free' iiowj through the piston ports I8,l while, when the piston moves outwardly during rebound operation, the valve disk will close to restrict the flow through the orices 23 for corresponding retardation or shock absorption during such rebound operation.

The arrangement shown on Figure 5 is the same as that shown on/Figure 4 except that a replenishing valve is interposed between the space in the working cylinder I0 and the chamber 33 in the housing'32. The inner wall of the housing 32 hasthe passageway 35 in communication with the threaded recess 36 inthe neck 34 of the housing. lThis threaded recess receives the cupshaped valve housing 31 having ports 38- in its bottom wall., -Within the housing is the valve disk 39 having theneck 40 extending inwardly therefrom, a spring 4| encircling this neck and abutting the Valve disk and the bottomfof the housing tending to hold the valve seated against the innery wall of the housing 32 to cover the passageway 35. The valve disk and neck has the l flow orifice 42 therethrough. When the piston i3 moves inwardly under compression or bound operation of the shock absorber, the valve disk I9 will be open for comparatively free iiow from the inner end of the cylinder I0 to the outer end thereof, the fluid displaced inthe outer end of the cylinder by the incoming piston rod I4V flowing through the ports I into the inner end of the cylinder, theresulting pressure against the valve disk 39 holding it closed- `so that theuid must flow through the more or less restricted orifice 42 into the chamber 33 for contraction of the compensator structure C. Upon outward movementof the piston under rebound operation of the shock absorber, the valve disk I9 will close to restrict the fluid flow to the orifices 2S and, as

' the piston rodis being withdrawn from the outer end of the cylinder I0, thecompensating structure C will expand and cause the fluidin the chamber 33 to exert ypressure against the valve disk 39 for opening thereof vfor exposure of the passageway 35. for comparatively free flow of fluidl from thecham-ber 33 into the inner end of the cylinder Ill and throughthe orifices 2B to compensate for the withdrawal of the piston rod. i Figures 6 and 7 embody the structure of Figure 5 except that a modified compensator structure is used. Like in Figure 5, the structure on Figure 6 embodies a cylinder housing 32 secured by its neck 34 to the cylinder IU and threaded at its outer end to the head II, the neck 34, like inthe structure of Figure A5, supporting the valve 39. Instead of flexible wallcompensators for containing air, like in Figures 1 to 5, in the arrangement of Figure 6 a compensator piston 43 is movable within the cylinder housing32 defining with the cylinder-wall. and the head AI Ithe air chamber- 44. The piston 43 is provided with packingii so that the chamber 44 isalways closed tocontan only air. Aspring Iii in the air chamber.44.re. sists outward vmovement of the vpiston 43 and tends to shift it inwardly. A valved. nipple plug 4'! is applied to the compensating cylinder housing 32 to communicate with the inner end thereof When theshock absorber is to be conditioned for service. hydraulic ii'uid is charged `in through the plug 41 while the main piston I3 .is at the outer end of the cylinder III, the compensating piston 43 being shifted outwardly by the oilpressure against resistance of the spring 46 foren inii tial Qompresson (ofthe. air inthe air chamber Figure 6 shows the main piston I3 at substantially the middle of the cylinder I with the compensator piston 43 at substantially the middle of the cylinder 32. Now as the piston I3 moves inwardly or outwardly during service operation of the shock absorber the compensator piston 43 will follow. During the compression or bound stroke of the piston i3 and movement of the piston rod I4 into the cylinder ill, the displaced fluid will now through the orifice 42 of the valve 39 into the compensating cylinder 32 to shift the compensator piston 43 outwardly to compensate for such displacement. During the rebound operation of the shock absorber the piston I3 moves outwardly to withdraw the piston rod and the expanding air in the chamber 44, assisted by the spring 43, will shift the piston 43 out to effect compensation for the withdrawal of the piston rod from the cylinder iii. Figure 7 shows the piston I3 at the inner end of the stroke and the corresponding position of the compensator piston 43 near the outer end of the cylinder housing In addition to compensation for movement of the piston rod into and out of the cylinder lll, the compensator structure will compensate for variation in volume of the hydraulic fluid due to temperature changes. The shock absorber hydraulic cylinder l in which the shock absorber piston i3 operates will therefore at all times be kept fully filled by the pressure exerted against the fluid at all times by the compensator structure. The shock absorber will therefore function with maximum efficiency in service where there is a wide range of temperature variation, as for example in aircraft landing gear, or on aircraft guns for damping gun recoil.

I have shown practical and efficient embodiments of various features of my invention but I do not desire to be limited to the exact construction and arrangement shown and described as changes and modifications may be made without departing from the scope of the invention.

I claim as follows:

l. A direct action shock absorber comprising a cylinder, a piston movable in the cylinder and having a rod extending therefrom to the exterior from one end of the cylinder, a housing part extending from the other end of the cylinder` said housing part defining a chamber for communication with said cylinder for the interflow of hydraulic fluid, compensating structure in said chamber defining a closed space containing air,

part of said compensating structure being movable in response to the pressure of fluid flowing into said chamber from said cylinder when lthe piston rod moves into the cylinder whereby the confined air is compressed and by its expanding tendency against the movable part of said compensating structure exerts pressure against the hydraulic uid to keep the cylinder filled during outward movement of the piston and withdrawal of the piston rod from the cylinder, valve means on said piston adapted to function to permit comparatively free ow from one side of the piston to the other during inward movement of the piston and the rod but to restrict the flow when the piston andr rod move outwardly, and valve means interposed between said cylinder and said chamber to function to resist flow from the cylinder into said chamber when the piston and piston rod move inwardly but to permit freer flow from the chamber into the cylinder when the piston and rod move outwardly whereby said valve means interposed between the cylinder and the chamber will control the resistance to inward movement of the piston and the valve means on the piston will control the resistance to outward movement thereof.

2. A direct action shock absorber comprising a cylinder, a piston movable in the cylinder and having a rod extending therefrom to the exterior from one end of the cylinder, means at the opposite end of the cylinder defining a chamber for communication with said cylinder for the interflow of hydraulic fluid, said cylinder andchamber being filled with hydraulic fluid, compensating structure within said chamber defining a closed space containing air, part of said compensating structure being movable in response to the pressure of fluid flowing into said chamber from said cylinder when the piston rod moves into the cylinder whereby the conned air is compressed and by its expansion tendency against the movable part of said compensating structure exerts pressure against the hydraulic fluid to keep the cylinder filled during outward movement of the piston and withdrawal of the piston rod from the cylinder, valve means on said piston for controlling the flow of fluid in said cylinder from one side of the piston to the other, and other valve means interposed between said cylinder and said chamber functioning to resist flow from the cylinder into said chamber when the piston and piston rod move inwardly but to permit freer ow from the chamber into the cylinder when the piston and rod move outwardly, said other valve means affording the sole iiow connection between said chamber and said cylinder whereby said other valve means controls resistance to inward movement of the piston.

3. A direct acting shock absorber comprising a cylinder having outer and inner end walls, a piston movable in said cylinder and having a rod extending therefrom to the exterior through said outer end wall, means associated with said inner end wall defining therewith a chamber for communication with said cylinder for the interflow of hydraulic fluid, compensating structure in said chamber defining a closed space containing air, part of said compensating structure being movable in response to the pressure of fluid displaced into said chamber from the cylinder when the piston rod moves into the cylinder whereby the confined air is compressed and by its expandingA tendency against the movable part of said compensating structure exerts pressure against the y hydraulic fluid to keep the cylinder filled during v return flow from said chamber when the pistonV and vrod move outwardly, said chamber except for said inner end wall valve means being closed f against flow communication with said cylinder whereby said valve means in said inner wall controls resistance to inward movement of the piston.

GERVASE M. MAGRUM. 

